Electrical submersible well pumps are commonly used for hydrocarbon well production. A typical pump assembly has an electrical motor with a seal section or protector on its upper end. The motor is filled with a dielectric lubricant. The seal section has an equalizer in communication with that lubricant. The equalizer is also in fluid communication with the well bore fluid for equalizing the pressure of the lubricant to that of the well bore fluid. Typically the seal section will also have a thrust bearing for absorbing downward thrust from the pump.
The pumping assembly may comprise one or more pumps and optionally a gas separator. The pumps are rotary pumps driven by a shaft of the motor. They may be either progressing cavity pumps or they may be centrifugal pumps having a large number of stages, each stage having an impeller and a diffuser. If a gas separator is employed, typically it has a rotary gas separating component for separating gas from the well fluid prior to the well fluid entering the pump.
A different connector is required on the lower end of the pump depending upon whether the pump is to connect directly to a seal section or to another component of the pumping assembly, such as a gas separator or another pump. The connectors are not readily interchangeable between pumps, thus the manufacturer may be required to keep both types. The reason for having both types of pumps has to do with whether the connector has intake ports or not. If the pump is connecting to an upstream component such as another pump or a gas separator, its connector would not have intake ports. If connecting directly to the seal section, the connector would need intake ports.
Referring to FIG. 1 as further explanation of the prior art, pump 10 is a centrifugal pump having a number of stages, each stage having an impeller 12 and a diffuser 14. Pump 10 has a connector 16 on its lower end for connecting to other components of the pumping assembly. Connector 16 has external threads 18 that connect to internal threads in the housing of pump 10. Connector 16 has a flange 20 on its lower end containing a pattern of holes 22, each for receiving a bolt 24. Connector 16 does not have any intake ports leading directly to the exterior for drawing in well bore fluid. The reason is that pump 10 is constructed to be a middle or upper tandem pump or one for connection to a gas separator below it. In those instances, the intake ports would be in lower connector of the lower tandem pump or in the lower connector of the gas separator.
If the manufacturer wishes to use pump 10 without connecting it to an upstream component, such as another pump or gas separator, he can do so by connecting it to a separate intake housing 26. Intake housing 26 is a separate sub that has intake ports 28 for well fluid to pass inward and up to pump 10. Intake housing 26 has its own short shaft 30 (intake shaft) mounted therein and which connects to pump shaft 32 by a coupling 34. A radial bearing (or bushing) 36 supports intake shaft 30 in housing 26. Radial bearing 36 does not form a seal. A coupling on the lower end of intake housing shaft 30 will connect it to a seal section shaft (not shown). Intake housing 26 has a radial flange 38 for bolting to the seal section (not shown). While combining pump 10 with intake housing 26 allows a manufacturer to use pump 10 either as a middle or upper tandem pump or as a single pump without a gas separator, it requires extra expense because of intake housing 26.